According to DIN 55946 (German Industrial Standard 55946) bitumens are a dark colored, semisolid to brittle, meltable, high molecular weight hydrocarbon mixture which are obtained in the careful working up of petroleums and the portions soluble in carbon disulfide of the natural asphalts as well as mineral wax and montan wax (see Rompp Lexikon der Chemie, 7th edition, page 377).
These types of materials which are designated in the English speaking areas (especially the USA) as asphalt are employed in admixture with powdered limestone, pulverized granite, ground basalt, ground diabase, and ground gabbro in the building of streets.
In this connection the use of natural asphalt is of especial significance. Natural asphalt can be employed in admixture with bituminous binders according to DIN 1995 to produce montan rich covering layers (e.g. cast asphalt, asphalt concrete, sand asphalt and asphalt mastic. A natural asphalt of this type is e.g. Trinidad-Epure which has the following composition:
Soluble Bitumen 53 to 55 wt. % PA1 Mineral portion 36 to 37 wt. % PA1 Remaining components 9 to 10 wt. %
(See Handbuch fur Strassenwesen, Planung-Bau-Verkehr-Betrieb 1979, Otto Elsner Verlagsgesellschaft, Darmstadt.)
Trinidad-Epure as well as the other known asphalts have the disadvantage that they frequently form hard, compact masses which first must be broken into small pieces in order to be homogenously miscible with the materials used as additives.
It has already been proposed to prepare asphaltite in particulate condition and to improve the flowability of the granulate through special additives.
There is known from Austrian Pat. No. 280876 a process according to which particulate asphaltite is treated with a wetting liquid, e.g. black liquor, and the finished product then sealed in air tight containers.
There are known from European Pat. No. 24513 powdered bitumen concentrates which contain in addition to bitumen 10 to 80 wt. % of synthetic silica.